1. Field of the Invention
The present invention relates to an image forming apparatus and particularly to an image forming apparatus with a function of saving power consumption.
2. Description of the Related Art
Image forming apparatuses of recent years generally include a normal mode and a sleep mode from the perspective of saving power consumption. The normal mode is a mode in which an image can be immediately formed when an image formation request is input and which has high power consumption. On the other hand, the sleep mode is a mode in which an image cannot be immediately formed when an image formation request is input and a preparation time is required until image formation and which has smaller power consumption than the normal mode.
In the case of waiting on standby in the normal mode, the image forming apparatus transitions from the normal mode to the sleep mode to suppress power consumption unless any operation is performed for a specified time. On the other hand, in the case of waiting on standby in the sleep mode, the image forming apparatus forms an image after returning from the sleep mode to the normal mode and preparing for image formation when an image formation request is input.
There is a prior art document which discloses an image forming apparatus including a normal mode and a sleep mode and having a function of saving power consumption. The image forming apparatus of this prior art document starts only functions necessary for an input image formation request when the image formation request is input and the image forming apparatus returns from the sleep mode to the normal mode. Specifically, when FAX data is received, only functions necessary for the output of the FAX data are started without starting a scanner function and the like. In this way, power consumption is saved.
However, in the image forming apparatus of the above prior art document, the functions necessary for the output of the FAX data are started even in such a state where an image cannot be immediately formed due to, for example, a paper-out condition when the image forming apparatus returns from the sleep mode to the normal mode upon receiving the FAX data.
This holds true for other functions such as a copy function and a printer function. In other words, functions necessary for an output corresponding to an input image formation request are started even in such a state where an image cannot be immediately formed when the image forming apparatus returns from the sleep mode to the normal mode upon receiving the image formation request. Then, unnecessary power is consumed to start the functions necessary for the output corresponding to the input image formation request despite the fact that an image cannot be immediately formed.